Monday, November 12, 2012

Pterosaur fact checking

I will keep this brief, since Mark already did a great job of responding to the media release from the recent Chatterjee et al. presentation. One thing to look for in any sort of functional morphology argument is whether the anatomy, the numbers, and the behavior all match up. One reason the Chatterjee et al. abstract is so immediately concerning is that their own information doesn't jive internally.

Example 1: one of their concerns with the quad launch hypothesis is clearance for the wings after launch. Now, I've calculated the expected clearance and everything seems fine, but that doesn't mean I'm right. Maybe someone will find an error at some point. What is clearly not going to be true, however, is the idea that keeping the feet on the ground (biped running launch) is going to give moreclearance than a leap. It simply isn't possible to get more clearance by not jumping (it might be true that jumping still isn't enough, but it's not going to be worse). So Chatterjee et al. have a mismatch between their own conclusions and their arguments with the competing model. The numbers and the behavior don't match up.

Example 2: Chatterjee et al. argue that pterosaurs can't work as scaled up bats, and argue instead that they should work like scaled up birds. Anatomically, pterosaurs don't match either of these, so the bat argument is a straw man, and the bird argument is moot. The anatomy and the behavior don't match up.

These are the sorts of arguments that raise red flags in scientific discourse. On a final note, there are some basic fact checking items that should be looked out for, such as claims about living animals. From the media story, Chatterjee is quoted as saying "Like albatrosses and the Great Kori bustards, which weigh 20 to 40 pounds, ground takeoff was agonizing and embarrassing for Quetzalcoatlus."

Aside from the problem with the pterosaur analogy, there is the obvious problem that Kori bustards don't have trouble taking off (though they might find it embarrassing; I haven't asked them). In fact, Kori bustards can leap into flight at a steep angle. Check this out. Yes, the bustard tries running to escape, first, but when pressed, it just leaps into the air. No big runway, no "agonizing" takeoff. In fact, there is no correlation between running launch and size in living birds or bats. More on that some other time, but in general, if a YouTube search quickly demonstrates that your commentary is flawed, that's a bit worrisome.

Thanks for the interesting comment. Reading the media, it seems that their model of take off for Albatross or Quetzalcoatlus is based on Orville or Wilbur form the Disney Bernard and Bianca ;-)). on a related, is there books or article accessible to non specialist about mechanism of flight or take off, ’ find always fascinating when you brought to us element as the near vertical take of of gallinacean.Alexandre

David Alexander's book on animal flight is relatively accessible, though it doesn't talk much about takeoff (perhaps not coincidentally, he is part of the "et al." in the Chatterjee et al. presentation on Quetzalcoatlus launch; perhaps takeoff isn't something he's worked on much). There are very general books/papers on takeoff, specifically, I am afraid to say.